narcissistic fiance

how the hell do y'all deal with someone like that. I can never win anything. always thinking so negatively. can't do shit together and enjoy anything cause he's always complaining...we have an almost two years old together mind you. so I feel the need to continue trying. it's been MONTHS probably a year of trying to work on things.it gets better for a week then starts back up and gets to it's worse where I'm about to leave. so stressed.